There is a storage apparatus configured as illustrated in FIG. 1. A base device 110 in this storage apparatus is connected to the host via a fiber channel or the like and functions even alone (i.e., with no add-on devices 120 connected thereto) as a storage. The add-on devices 120 have a plurality of disk drives incorporated therein and are daisy-chained to the base device 110 to implement a large-capacity storage system.
The total storage capacity of this storage apparatus may be increased, therefore, by adding add-on devices 120. When installing this storage apparatus in a large-scale data center or the like, the maximum number of add-on devices 120 are sometimes incorporated in the storage apparatus such that add-on devices 120 does not have to be installed in the future.
In such a case, the add-on devices 120 that are incorporated in the storage apparatus for future extension of the storage capacity and are currently not used at all (referred to hereinafter as extra add-on devices 120) consume electric power. It is desirable, therefore, to reduce the power consumption by the extra add-on devices 120, but, in conventional storage apparatus, there is no way but to manually turn off the power switches of the add-on devices 120 to reduce the power consumption by the extra add-on devices 120.
Japanese Laid-open Patent Publication Nos. 2008-90352 and 2008-276341 discuss the power consumption control for a storage apparatus (system).
Problems to be solved by the disclosed technology are to provide a storage system that automatically controls the power consumption by the extra storage units in the storage system and to provide a power consumption control method for the storage system to automatically control the power consumption by the extra storage units in the storage system.